Porcelain enamel coating



Aug. 29, 1967v J A. HoLcoMB 3,338,732

INVENTOR.

JAMES A. HOLCOMB l ATTORN S United` States Patent Office 3,338,732 Patented Aug. 29, 1967 3,338,732 PORCELAIN ENAMEL COATING James A. Holcomb, Birmingham, Mich., assigner to Wolverine Porcelain Enameling Company, Detroit, Mich., a corporation of Michigan Filed4 Oct. 7, 1964, Ser. No. 402,287 7 Claims. (Cl. 117-26) This invention relates to porcelain enamel coatings and a method for applying same, and more particularly to a porcelain enamel coating for a metallic object or surface having a simulated aggregate finish.

In the manufacture and coating of many metallic objects it is not uncommon to provide a smooth and glossy .finish on the object to obtain a pleasant appearan. Such finishes are normally formed by the porcelain enamel process to provide a hard and durable finish; The metallic object is first covered with a ground coat of porcelain enamel material and then fusing a colored cover coat over the ground coat. The resultant finish may range from an extremely high gloss to a low gloss as desired and, being formed of a vitreous material, is extremely hard and long lasting.

Because of the gloss on the finished coating, the surface must be kept clean to prevent blemishes, or other foreign substances from discoloring or spoiling the effect of the'smooth glossy finish. Furthermore, in exterior structures, weathering often has some undesirable streak- .ing or other adverse effect on the high gloss.

coat is still wet and before fusing the cover coat, and

then applying Aan over-spray of glaze or cover coat over the colored cover coat and the particles to secure the particles in place. The resultant .structure is a simulated aggregate or rough finish which breaks up the high gloss y'surface and which presents a pleasant appearance to the observer. At the same time, the rough appearance of the coating helps to hide the surface blemishes and discolora- -tions that result from weathering and the like. The coating is structurally sound and the particles are positively held in place by the fused glaze coat so that the particles do not fall or chip out ofthe coating structure.

These and other advantages will become more apparent from the following description and drawing in which:

The single ligure is a cross-sectional view of a portion of a metallic object having the composite coating thereon.

The porcelain enameling process per se is Well known in the prior art and this invention makes use of the various well known processes and materials. Generally speaking, and as set out in The Ready Remedier-A Manual of Porcelain Enameling by Karl Turk, Copyright 1931 by The Porcelain Enamel and Manufacturing Company, the porcelain enameling process includes the application of a ground coat of porcelain enamel materials over the metallic object, the object being in the form of a sheet metal panel, sheet metal stamping, casting, or the like. The porcelain enamel ground coat is fused at an elevated temperature to the metallic object. A porcelain enamel cover coat is then applied over the ground coat, the cover coat being provided with various oxides and other materials to produce a desired color on the structure being coated. After the application of the cover coat the object is again fused at an elevated temperature to fuse the cover coat to the ground coat. Further applications of colored cover coats may be applied if desired, each successive coat being heated to its fusing temperature in order to provide a proper porcelain enamel finish.

Referring now to the drawing, the metallic object is indicated by the numeral 10 and may be in any suitable shape or form. For purposes of illustration, object 10 is illustrated as a sheet metal panel. After the panel 10 has been thoroughly cleaned, pickled, and otherwise prepared for the porcelain enameling process, the ground coat materials are sprayed or otherwise applied to the surface of the object 10. The ground coat is then fused at an elevated temperature to provide the proper ground or foundation coat 12 in the usual manner.

The next operation is -to apply a cover coat of porcelain enamel material which may be applied by spraying or dipping. While the applied cover coat is still wet, particles 14 of finite size and of a suitable inorganic material such as fine silica, are sprinkled over the cover coat. The particles partially embed themselves in the wet cover coat, and are of such size as to project outwardly therefrom. The object is again heated to the fusing temperature to fuse the cover coat material into a porcelain enamel layer 16, properly fused to the ground coat 12 and to the portions of the particles 14 which are embedded therein.

The final operation is -to provide an over-spray of glaze or cover coat 18 of porcelain enamel. The porcelain enamel materials are first sprayed or otherwise applied over the surface of the cover coat 16 and the exposed portions of the silica particles 14. The over-spray or glaze coat is then raised to the elevated temperature to properly fuse the material to the exposed portions of the silica particles 14 and to the exposed surface of the cover coat 16. The over-spray `or glaze coat may be colored as is the cover coat, by applying the proper oxides and other materials in the Well known manner. Alternatively, the overspray coat may be clear or uncolored, being prepared in the well known manner.

The resultant composite coating is one that has all the' tains the silica particles 14 in place in the coating.

Should it be desirable to provide several layers of the cover coat 16, in order to provide the proper color or pattern to the finish, such additional coats are applied between the ground coat and the cover coat 16 having the silica particles 14 disposed therein. In other words, the top or last layer of cover coat 16 is sprinkled with the particles before it is dry, to partially embed the particles in the porcelain enamel coating.

It is also possible to eliminate entirely the ground coat 12. Depending upon the use and location of the object 10, the colored cover coat 16 may be fused directly to the metallic object and the over-spray coat 18 fused over such cover coat and the particles 14 embedded therein.

Thus, a porcelain enamel composite coating is provided for a metallic object which is extremely hard and durable but which does not have the high gloss or shine normally associated with porcelain enamel and further has an aggregate-like finish or texture which has not heretofore been available.

Numerous modications and alterations in the composite coating structure will become apparent to those having skill in the art after having had reference to the foregoing description and drawing. However, it is not intended to limit the scope of the invention by the foregoing description and drawing but by the scope of the appended claims in which:

I claim:

1. An article having a rough aggregate finish comprising a metallic structure having thereon a composite coating comprising:

a porcelain enamel ground coat on said subject;

a porcelain enamel cover coat over said ground coat and having particles of inorganic material fused therein, said particles being of a size to extend outwardly from said cover coat;

and a porcelain enamel over-spray coat over said cover coat and said particles.

2. An article having a rough aggregate finish comprising a metallic structure having thereon a composite coating comprising:

a porcelain enamel ground coat applied on said structure and fused at an elevated temperature;

a porcelain enamel cover coat sprayed on said ground coat and having particles of inorganic material and of sufficient size to extend outwardly therefrom, said cover coat and said particles being fused at an elevated temperature;

and a porcelain enamel over-spray sprayed over said cover coat and said particles and fused at an elevated temperature.

3. An article having a rough aggregate finish comprising a metallic structure having thereon a composite coating comprising:

a porcelain enamel ground coat on said structure;

a porcelain enamel cover coat over said ground coat;

a sprinkling of particles of inorganic material fused in said cover coat, said particles being of sucient size to extend outwardly from said cover coat;

and a porcelain enamel over-spray coat over said cover coat and said particles to secure said particles in said coating.

4. An article having a rough aggregate nish comprising a metallic structure having thereon a composite coating comprising:

a porcelain enamel ground coat fused to said structure;

a porcelain enamel cover coat 'fused to said ground coat;

a sprinkling of silica particles fused in said cover coat and being of sucient size to extend outwardly therefrom;

and a porcelain enamel over-spray fused to said cover coat and said particles to maintain said particles in said coating.

5. An article having a rough aggregate finish comprising a metallic structure having thereon a composite coating comprising:

a porcelain enamel cover coat on said structure; v

particles of inorganic material fused in said cover coat and being of sufiicient size to extend outwardly therefrom;

and a porcelain enamel over-spray coat over said cover coat and said particles and fused thereto.

6. A method of forming a porcelain enamel coating having a rough aggregate iinish toa surface of a metal panel comprising the steps of:

covering said surface of said panel with a ground coat and `fusing said ground coat at an elevated temperature;

covering said ground coat with a cover coat of porcelain enamel material; sprinkling particles of silica of suicient size to extend outwardly from said cover coat on said cover coat and allowing the particles to partially embed in said cover coat; v

heating said cover coat and said particles to an elevated temperature to fuse said cover coat to said ground coat and to said particles;

and covering said cover coat `and the exposed portions of said particles with an over-spray coat of porcelain enamel and fusing said over-spray coat thereto at an elevated temperature.

7. A method of forming a porcelain enamel coating having a rough aggregate inish to a surface of a metal panel comprising the steps of:

covering said surface with la cover coat of porcelain enamel material;

sprinkling particles of inorganic material and of sucient size to extend outwardly from said cover coat on said cover coat when said cover coat is in uid condition to partially embed said particles in said cover coat;

heating said panel and said cover coat and said particles to an elevated temperature to fuse said cover coat to said panel and to said particles;

and covering said cover coat and the exposed portions of said particles with an over-spray coat of porcelain enamel and fusing said over-spray coat thereto.

References Cited UNITED STATES PATENTS 1,373,217 3/1921 Warman 117--16 1,784,392 12/ 1930 BoWland.

2,337,691 12/1943 Stettmius et al. 117--16 2,466,682 4/1949 Bryant 117-29 X 2,624,823 1/ 1953 Lytle 117--70 2,708,172 5/1955 Robson et al. 117-70 2,828,218 3/1958 Zimmerman 117-70 2,864,721 12/ 1958 King et al. 117--70 ALFRED L. LEAVTTT, Primary Examiner.

RALPH S. KENDALL, Examiner. 

1. AN ARTICLE HAVING A ROUGH AGGREGATE FINISH COMPRISING A METALLIC STRUCTURE HAVING THEREON A COMPOSITE COATING COMPRISING: A PORCELAIN ENAMEL GROUND COAT ONSAID SUBJECT; A PORCELAIN ENAMEL COVER COAT OVER SAID GROUND COAT AND HAVING PARTICLES OF INORGANIC MATERIAL FUSED THEREIN, SAID PARTICLES BEING OF A SIZE TO EXTEND OUTWARDLY FROM SAID COVER COAT; AND A PORCELAINENAMEL OVER-SPRAY COAT OVER SAID COVER COAT AND SAID PARTICLES. 